Without limiting the scope of the invention, its background is described in connection with patch antennas. One system that uses patch antennas is taught in U.S. Pat. No. 7,006,044, issued to Choi, et al., for a microstrip patch antenna using MEMS technology. Briefly, a microstrip patch antenna is formed by using a microelectro-mechanical system fabrication technology. The microstrip patch antenna includes: a substrate provided with a ground formed on a bottom surface of the substrate, a feeding line formed on a top surface of the substrate for feeding an electric power, a coupling stub formed on the top surface of the substrate and electrically connected to the feeding line, a plurality of supporting posts erected on the top surface of the substrate, and a radiating patch formed on the supporting posts, thereby forming an area of air between the radiating patch and the top surface of the substrate.
Another system is taught in U.S. Pat. No. 5,970,393, issued to Khorrami, et al., for an integrated micro-strip antenna apparatus and a system that uses wireless communications for sensing and actuation purposes. Briefly, a system is taught for using a number of micro-strip antenna apparatus embedded in or mounted on the surface of a structure for enabling wireless communication of sensed and actuation signals. The micro-strip antenna apparatus may include smart materials or other substrates. If only a sensed operation is desired, the micro-strip antenna apparatus may be fabricated from only passive elements or materials. Furthermore, a micro-strip antenna apparatus is provided which enables simultaneous transmission/reception of sensing and actuation signals.
Finally, United States Patent Application No. 20070276294, filed by Gupta, et al. (now U.S. Pat. No. 8,070,695, teaches a strain monitoring system and apparatus. Briefly, a system for monitoring strain as an indicator of biological conditions, such as spinal fusion, glucose levels, spinal loading, and heart rate is disclosed. The system includes an inter-digitated capacitor sensor, and RF transmitter, and an associated antenna, all of which are microminiature or microscopic in size and can be implanted in a biological host such as a human or animal. An inductively coupled power supply is also employed to avoid the need for implantation of chemical batteries. Power is provided to the sensor and transmitter, and data is transmitted from the sensor, when an external receiving device, such as a handheld RF ID type receiver, is placed proximate the location of the implanted sensor, transmitter and inductively coupled power supply. The implanted sensor, transmitter and inductively coupled power supply can be left in place permanently or removed when desired.